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Bone defects such as through fractures or other causes can be treated with autologous bone grafts (i.e., bone taken from another part of a patient's body). The graft can act as a scaffold to aid in the bone regeneration process. This approach to treating bone defects, however, has several drawbacks including the requirement for additional surgery and the morbidity to the donor site.
As an alternative to autologous bone grafts, various biocompatible synthetic bone fillers have been developed such as the calcium phosphate cements (CPCs) and the acrylic bone cement polymethylmethacrylate.
Synthetic bone fillers have additionally been investigated as drug delivery systems. For example, zoledronate-impregnated CPC blocks implanted in the greater momentum were found to decrease bone turnover and to restore bone architecture in ovariectomized rats. Treating a localized bone defect in this fashion, however, results in potentially unnecessary systemic exposure to a drug. In another study, simvastatin β-hydroxy acid in CPC was released over one week and promoted osteogenesis using in vitro assay systems. This relatively quick release of drug over just one week may be of insufficient duration where the promotion of bone growth is required for longer periods of time.
Thus, there exists a need for improved compositions, systems, and methods for locally delivering a bone-repairing drug over extended periods of time to promote bone growth and repair bone defects.